embeddedTemplateDir empty when using custom templates

when I try to define custom templates, the generator does not get the embedded templates
When analyzing the generator code, I noticed that the embeddedTemplateDir variable is not initialized in this case

[INFO] Skipped overwriting gradle.properties as the file already exists in /home/mmedjahed/basic-rest-client/target/generated-sources//gradle.properties
[INFO] Skipped overwriting AndroidManifest.xml as the file already exists in /home/mmedjahed/basic-rest-client/target/generated-sources/src/main/AndroidManifest.xml
[ERROR]
java.lang.RuntimeException: Could not generate model 'AuthRequest'
at io.swagger.codegen.v3.DefaultGenerator.generateModels(DefaultGenerator.java:451)
at io.swagger.codegen.v3.DefaultGenerator.generate(DefaultGenerator.java:779)
at io.swagger.codegen.v3.maven.plugin.CodeGenMojo.execute(CodeGenMojo.java:547)
at org.apache.maven.plugin.DefaultBuildPluginManager.executeMojo(DefaultBuildPluginManager.java:134)
at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:207)
at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:153)
at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:145)
at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:116)
at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:80)
at org.apache.maven.lifecycle.internal.builder.singlethreaded.SingleThreadedBuilder.build(SingleThreadedBuilder.java:51)
at org.apache.maven.lifecycle.internal.LifecycleStarter.execute(LifecycleStarter.java:128)
at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:307)
at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:193)
at org.apache.maven.DefaultMaven.execute(DefaultMaven.java:106)
at org.apache.maven.cli.MavenCli.execute(MavenCli.java:863)
at org.apache.maven.cli.MavenCli.doMain(MavenCli.java:288)
at org.apache.maven.cli.MavenCli.main(MavenCli.java:199)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.codehaus.plexus.classworlds.launcher.Launcher.launchEnhanced(Launcher.java:289)
at org.codehaus.plexus.classworlds.launcher.Launcher.launch(Launcher.java:229)
at org.codehaus.plexus.classworlds.launcher.Launcher.mainWithExitCode(Launcher.java:415)
at org.codehaus.plexus.classworlds.launcher.Launcher.main(Launcher.java:356)
Caused by: java.io.FileNotFoundException: /home/mmedjahed/basic-rest-client/src/main/resources/templates/handlebars/Java/model.mustache
at com.github.jknack.handlebars.io.URLTemplateLoader.sourceAt(URLTemplateLoader.java:70)
at com.github.jknack.handlebars.Handlebars.compile(Handlebars.java:438)
at com.github.jknack.handlebars.Handlebars.compile(Handlebars.java:419)
at io.swagger.codegen.v3.templates.HandlebarTemplateEngine.getHandlebars(HandlebarTemplateEngine.java:48)
at io.swagger.codegen.v3.templates.HandlebarTemplateEngine.getRendered(HandlebarTemplateEngine.java:24)
at io.swagger.codegen.v3.DefaultGenerator.processTemplateToFile(DefaultGenerator.java:795)
at io.swagger.codegen.v3.DefaultGenerator.generateModels(DefaultGenerator.java:438)
... 24 more
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 1.415 s
[INFO] Finished at: 2020-05-11T12:56:23+02:00
[INFO] Final Memory: 19M/306M
[INFO] ------------------------------------------------------------------------

Start in DefaultGenerator, where embeddedTemplateDir is used when custom templates are configured, and trace the lookup into HandlebarTemplateEngine for model.mustache. Confirm generation with custom templates can still resolve embedded templates without the reported FileNotFoundException.